Internal combustion engine

ABSTRACT

A cylinder head for an internal combustion engine wherein intake openings to the cylinder are partly surrounded by a mask formed by a material projection of the top face of the combustion chamber, a contour of the mask having a flat main section of maximum height between an ascending and descending flank and being asymmetrical in a developed view.

The invention relates to an internal combustion engine comprising acylinder head with at least one intake port and at least one fuelinjection device per cylinder, which extends into the combustionchamber. The invention also relates to a method for operating aninternal combustion engine with at least two exhaust valves percylinder, where in at least one operating region of the engine exhaustgas is recirculated into the combustion chamber from the exhaust portsvia the exhaust valves, and where a swirl flow is generated in thecombustion chamber due to differing closing times of the exhaust valves.Furthermore the invention relates to an internal combustion enginecomprising a cylinder head with at least two intake and two exhaustvalves per cylinder, and with a valve actuating device which permitsclosing of the exhaust valves at different times. The invention furtherrelates to a cylinder head for an internal combustion engine with atleast two intake ports per cylinder opening into the combustion chamber,each intake port being provided with a valve seat in the area where itopens into the combustion chamber, and the openings being partlysurrounded by masks formed by material projections of the top face ofthe combustion chamber.

From DE 103 26 054 A1 there is known an internal combustion engine witha cylinder head, an injection device injecting fuel directly into thecombustion chamber, and two intake ports per cylinder, where the intakeopenings are provided with rib-shaped masks surrounding the disks of theintake valves semi-circularly and facing the injection nozzle. Thesemasks deflect the combustion air flow approximately in parallel to thelateral fuel jet in order to initiate a tumble flow in the combustionchamber. In the area of the fuel jet at least one of the masks isdivided by a gap, exposing the fuel jet immediately to part of theinflowing combustion air. This should increase the efficiency of theinternal combustion engine and improve ignition reliability. The gapextending over the whole height of the mask will however impair theeffect of the mask.

In conventional direct-injection internal combustion engines theinjection device extends into the combustion chamber. The exposedsituation of the injector tip causes increased wear.

From U.S. Pat. No. 6,502,541B2 there is known an internal combustionengine in which exhaust gas can be recirculated into the combustionchamber via the exhaust valves. Internal exhaust gas recirculation isused to improve fuel consumption especially in part-load operation. Togenerate a swirl of the recirculated exhaust gas in the combustionchamber the exhaust valves are closed at different times. Differentclosing times are achieved by a phase shift in the timing of the twoexhaust valves. The exhaust valves are thus also opened at differenttimes. In order to adjust the valve timing for both valves independentlyof each other complex technology is required.

In U.S. Pat. No. 5,870,993 another internal combustion engine isdisclosed with two intake and two exhaust valves per cylinder, in whichinternal exhaust gas recirculation from the exhaust ports into thecombustion chamber can be achieved by shifting the lifting curves of theexhaust valves. By masks in the area of the two exhaust ports a swirlmay be imparted to the recirculated exhaust gas in the combustionchamber. The masking of the two exhaust ports is disadvantageous at fullload.

From EP 0 764 770 B1 there is known a cylinder head which is partiallyprovided with masks in the area where the intake ports open into thecombustion chamber, wherein the walls of the intake ports on one side ofthe opening are configured in such a way that the flow cross-section atlow lift of the intake valve is narrowed over an angle region ofapproximately 180°. At low-load or part-load operation this creates atumble flow which arises from the intake ports.

U.S. Pat. No. 4,974,566A discloses an internal combustion engine withtwo intake ports opening into the cylinder, whose walls are configuredsuch that at small valve lifts the intake cross-section for the flowthrough the intake ports is narrowed in a region defined by a certainangle around the movement axis of the intake valve in such a way that atsmall valve lifts a tumble flow is generated. For large valve lifts theintake cross-section extends along the whole periphery of the valves,which permits satisfactory filling of the cylinder. In the part-loadregion the engine is operated with small valve lifts, thus giving goodthermodynamic conditions for combustion due to the prevailing tumbleflow. At full load the engine is operated with full valve lifts, thusachieving sufficient filling of the cylinder and sufficient torque.

It is the object of the present invention to minimize the abovementioned wear of the injection device in an internal combustion engine.Furthermore, the forming of deposits in the area around the entry of theinjection device into the combustion chamber is to be avoided. A furtheraim of the invention is to achieve good fuel economy at part loadwithout impairing full load performance. Furthermore it is an object ofthe invention to design a cylinder head with which combustion conditionsespecially at part load may be improved and emissions may be furtherreduced.

The invention achieves these aims by providing that the top of thecombustion chamber has an injector pocket in the area where theinjection device enters the combustion chamber, preferably with at leastone arrangement of scavenging passages opening into the injector pocket.Scavenging air enters the injector pocket via the scavenging passagearrangement, thus preventing the formation of deposits. The method ofscavenging the injector will not, or only slightly, impair theeffectiveness of the masking.

In a first variant of the invention, which has no negative influence onthe effectiveness of the masking, it is provided that the scavengingpassage arrangement is located in the region of at least one squishsurface of the combustion chamber top preferably formed by the cylinderhead. Preferentially it is provided that the scavenging passagearrangement has at least one scavenging passage which starts from a flatentry area and opens into the injector pocket via a nozzle region.Advantageously the depth of the scavenging passage increases in thedirection towards the injector pocket. Preferably the scavenging passagenarrows in the form of a nozzle, thus causing the scavenging air toenter the injector pocket with high flow velocity. As the pistonapproaches upper dead center scavenging air is pressed via the squishsurface into the scavenging passage arrangement and further into theinjector pocket, thus cleaning out deposits from the injector pocket.

In a second variant of the invention it is provided that the scavengingpassage arrangement departs from an intake port, preferably from thevalve seat area of the intake port. If at least one intake port isfurnished with a mask, it is of particular advantage if the scavengingpassage arrangement is formed into the mask. Advantageously in this caseat least one scavenging passage is positioned essentially radiallyrelative to the intake port between the intake port and the entry pointof the injection device.

In a particularly simple variant of the invention it is provided thatthe scavenging passage has a cross-section which is open towards thecombustion chamber and is configured preferably as a slot or a groove.The slot or groove may be machined into the cylinder head in a simplemanner. It is also possible, however, that the scavenging passage atleast partly has a closed cross-section and is preferably formed by abore. Preferentially it is provided that the scavenging passagearrangement has a certain distance from the bottom of the mask. Theeffective mechanism of the mask will be much less impaired by thismeasure than by a gap in the mask extending over its whole height, asshown in DE 103 26 054 A1.

It is provided by the invention that the longitudinal axis of at leastone scavenging passage forms an angle greater than 0°, preferablybetween 30° and 60°, with a plane defined by the cylinder axis and theaxis of the injection device.

To achieve a sufficient swirl effect it is advantageous if the maskextends around the intake port over an angle of 150° to 180°. In thisinstance the height of the mask should be between 1.5 mm and 4 mm.Preferably it is provided that the distance from the mask to the rim ofthe valve disk is about 0.3 mm to 0.7 mm.

To improve on fuel consumption at part load without impairing full-loadperformance it is proposed that the two exhaust valves be opened fordiffering lengths of time, both exhaust valves preferably opening at thesame time. Via a phase adjuster the opening point of the exhaust valvesmay be shifted synchronously. In the case of cam-controlled operation inparticular, it may be provided that the exhaust valves have exhaustvalve lift curves of differing length.

The invention is also suitable for cam-less operation, however.

By simultaneously opening both exhaust valves a relatively large volumeof exhaust gas may be fed into the exhaust ports at the beginning of theexhaust stroke. In this way a favourable emptying behaviour of thecombustion chamber may be achieved with minimal throttling losses. Thiswill result in a high power yield, especially at full load.

In the context of the invention it is provided that the differencebetween the closing points of the exhaust valves is 10° to 80° of crankangle, and preferably 20° to 60° of crank angle, a first exhaust valvepreferably being closed immediately after upper dead center of thecharge exchange process and a second exhaust valve being closed at 20°to 60° crank angle after upper dead center of the charge exchangeprocess. The closing point is here defined as that point in time atwhich the exhaust valve has a residual lift of 1 mm. Differing closingpoints will cause swirl to be generated when exhaust gas is sucked backinto the cylinder from the exhaust duct. To achieve strong swirlcomponents it is advantageous if the recirculated exhaust gas is guidedover a flow guiding surface formed by a mask in the area of at least oneexhaust valve. The mask may be provided in the area of one exhaust valveonly. In this way flow losses during outflow from the cylinder at fullload may be kept small. In order to achieve a sufficient swirl effect itis advantageous if the mask extends around the center of the exhaustport through an angle of approximately 150° to 180°. The height of themask should be 1.5 mm to 4 mm. Preferably it is provided that thedistance of the mask from the rim of the valve disk is 0.3 mm to 0.7 mmapproximately.

The different closing times of the exhaust valves may be realised by anasymmetrical shape of the cam of at least one exhaust valve.Preferentially it is provided that each exhaust valve is actuated by itsown cam, with the cams having different closing flanks. Furthermore itmay be provided that the cams have identical opening flanks and/oridentical maximal cam lobes.

In addition, the swirl in the combustion chamber due to the intake flowfrom the intake ports can be increased by asymmetrical intake ports, oneintake port being preferably configured such that it can be closed down.

Combustion conditions and emissions can be improved if the contour ofthe mask of at least one intake port has a flat main part of maximumheight between an ascending and a descending flank and in a developedview is of asymmetrical shape, ascending and descending flankspreferably having different slope angles.

It is particularly advantageous if the flank of the profile closer tothe combustion chamber wall has a smaller slope than the flank nearer tothe center of the combustion chamber. The intake flow may thus bespecifically guided to a central cylinder region generating a tumbleflow in the direction of the piston axis.

It has been found by experiments that a particularly high stability ofcombustion can be attained if the mask of each port extends over anangle of 120° to 210°, measured around the center of the port opening,and preferably over an angle between 160° and 180°. Preferentially it isprovided that at each port a main axis running approximately through themiddle of the main part of the mask forms an angle of 70° to 120°,preferably between 80° and 110°, with a straight reference line runningthrough the centers of the port openings.

The height of the mask is chosen such that at partial valve lift theopening of each intake port is laterally covered on the intake side. Atfull valve lift the intake valve is beyond the mask and the full intakecross-section is available. The height of the mask is 1.2 mm to 3.5 mmapproximately, and preferably 1.6 mm to 2.5 mm, and even more preferably1.6 mm to 2.2 mm. In order to avoid heavy throttling of the intake flowespecially under full load it is of advantage if a clearance is providedbetween the mask and the valve disk, which should not exceed a quarterof the height of the mask, preferably.

In a particularly preferable variant of the invention it is providedthat the depth of the injector recess is at most about equal to theheight of the mask. By positioning the injector orifice in the area ofthe injector recess of the mask, the injector nozzle may extendrelatively deeply into the combustion chamber. The depth of the injectorrecess will thus correspond to the height of the mask at most. It isfurthermore of advantage if the injector recess is at a distance fromthe wall of the mask, this distance being at least 1 mm. This minimumdistance between injector recess and wall of the mask will avoidnegative influence on the intake flow.

The invention will now be described in more detail with reference to theenclosed drawings. There is shown in

FIG. 1 a cylinder head of an internal combustion engine according to theinvention in a first variant, as seen from the side of the combustionchamber;

FIG. 2 a scavenging passage arrangement of an internal combustion engineaccording to the invention in an oblique view, in a second variant;

FIG. 3 a scavenging passage arrangement of an internal combustion engineaccording to the invention in a third variant;

FIG. 4 a scavenging passage arrangement of an internal combustion engineaccording to the invention in a fourth variant;

FIG. 5 a scavenging passage arrangement in a section along line V-V ofFIG. 1 and FIG. 2;

FIG. 6 a scavenging passage arrangement of an internal combustion engineaccording to the invention in a fifth variant, in an oblique view;

FIG. 7 the scavenging passage arrangement of FIG. 6 in a section alongline VII-VII of FIG. 6;

FIG. 8 a cylinder head of an internal combustion engine according to theinvention in a sixth variant, as seen from the side of the combustionchamber;

FIG. 9 the cylinder head in a section along line XI-XI in FIG. 8;

FIG. 10 a variant of a scavenging passage in cross-section;

FIG. 11 another variant of a scavenging passage in cross-section;

FIG. 12 a further variant of a scavenging passage in cross-section;

FIG. 13 the valves of a cylinder head of an internal combustion engineaccording to the invention;

FIG. 14 the cylinder head in a section along line XIV-XIV of FIG. 13with the exhaust valve opened;

FIG. 15 the cylinder head in a section analogous to that of FIG. 14 withthe exhaust valve closed;

FIG. 16 a valve lift/crank angle diagram;

FIG. 17 the developed contour of the mask of an intake port;

FIG. 18 the cylinder head according to the invention as seen against thecombustion chamber top face;

FIG. 19 an oblique view of the openings of two intake ports of thecylinder head;

FIG. 20 the cylinder head in a section along line XX-XX of FIG. 18; andin

FIG. 21 the mask in a section detail analogous to FIG. 20;

Parts with identical function are referred to by identical referencenumerals.

FIG. 1 shows a cylinder head 1 of an internal combustion engine as seenfrom inside the combustion chamber. The cylinder head 1 has for eachcylinder 2 two intake ports 4 served by intake valves 3. The exhaustports are not shown in the figures to keep the drawings uncluttered.

In the area of a transversal plane 5 between the intake ports 4 aninjection device 6 enters the combustion chamber. The axis 6′ of theinjection device 6 is inclined relative to the cylinder axis 9. In theentry area or mouth 6 a of the injection device 6 an injector pocket 7is located in the cylinder head 1. An ignition device in the area of thecylinder axis 9 is indicated by reference numeral 8.

The intake ports 4 are partly screened by masks 20 in order to initiatea tumble flow in the combustion chamber. The mask 20 extends through anangle α of between 150° and 180° around the center 4 a of the intakeport 4. The height HM of the mask 20 is 1.5 mm to 4 mm—as measured fromhalf the height h of the valve disk rim 3 a of the closed intake valve3. The distance a between the mask 20 and the valve disk rim 3 a is 0.3mm to 0.7 mm. Due to the mask 20 deposit-prone regions with low localflow velocities occur in the area of the injector pocket 7, especiallybetween the intake ports 4 and the injector entry 6 a.

To combat these deposits an arrangement of scavenging passages 10 isprovided for each intake port 4, which open into the injector pocket 7.The scavenging passage arrangements 10 presented in FIGS. 1 to 7comprise at least one scavenging passage 10 a, an inlet region 11 and anozzle region 12 each. The inlet region 11 has small depth t butrelatively large width b and is located in the area of a squish surface13 of the top face 22 of the combustion chamber formed by the cylinderhead 1. The width b of the scavenging passage arrangement 10 decreasestowards the nozzle region 12 and attains its minimum at the opening intothe injector pocket 7. The depth t increases continuously from the inletregion 11 towards the nozzle region 12 and attains its maximum at theopening into the injector pocket 7. In plan view the arrangement 10 ofscavenging passages may be pear-shaped, club-shaped or bat-shaped asseen in FIGS. 2 to 4 and 6. In the variants shown in FIGS. 2 to 5 thescavenging passage 10 a of the scavenging passage arrangement 10 has across-section that is open towards the combustion chamber.Alternatively, the scavenging passage 10 b of the scavenging passagearrangement 10 may have a closed cross-section, as shown in FIGS. 6 and7, and may be inclined relative to the plane 21 of the cylinder headgasket.

As the piston of the internal combustion engine, which is not shown inthe drawings, approaches upper dead center, the gas enclosed in thecombustion chamber is pressed by the squish surfaces 13 into the inletregion 11 of the scavenging passage arrangement 10 and flows through thescavenging passage 10 a or 10 b into the injector pocket 7, carrying offdeposits due to the high flow velocity.

The variants shown in FIGS. 8 and 9 differ from the variant describedabove by the scavenging passage arrangement 10 being located in the areaof the intake port 4 in the form of an opening in the mask 20. Thescavenging passage arrangement 10 may in this case have at least onescavenging passage with closed cross-section, for instance formed by abore 10 b (FIG. 10), and/or at least one scavenging passage 10 a with across-section open towards the combustion chamber (FIGS. 11, 12). Theopen scavenging passage 10 a may be formed by a slot (FIG. 11) or agroove (FIG. 12) at a certain distance from the bottom 20 a of the mask20. In this variant the scavenging passage arrangement 10 is positionedbetween the entry 6 a of the injector device 6 and the intake port 4.

When the intake valve 3 opens scavenging air can flow through thescavenging passage 10 a, 10 b from the intake passage into the injectorpocket 7, removing deposits from the injector pocket 7.

The longitudinal axis 10′ of the scavenging passage arrangement 10 formsa angle β of 30° to 60° with a transversal plane 5.

FIG. 13 shows a cylinder head 101 in a view from the combustion chambertowards the cylinder head bottom 102 of a cylinder 103. For eachcylinder 103 two intake ports 104, 105 and two exhaust ports 106, 107open into the combustion chamber, which is not otherwise visible. Viathe intake ports 104, 105 the combustion chamber communicates withintake passages and via the exhaust ports 106, 107 with exhaustpassages, neither of which are shown in the drawing. The intake ports104, 105 respectively the exhaust ports 106, 107 are controlled byintake valves 104 a, 105 a, respectively by exhaust valves 106 a, 107 a.

To improve on fuel consumption, in particular when the internalcombustion engine operates at part load, internal exhaust gasrecirculation may be used. Such internal exhaust gas recirculation isrealized by sucking back exhaust gas from the exhaust passages into thecombustion chamber subsequent to the exhaust stroke near upper deadcenter OTW of the gas exchange phase. In this instance a strong swirl isdesirable in the combustion chamber in order to improve combustionconditions and emissions. This swirl is generated by closing the exhaustvalves 106 a, 107 a at differing points in time. A further increase ofswirl may be achieved by a mask 108 in the area of at least one exhaustport 106. In order to keep the flow losses small at full load duringoutflow from the cylinder 103, the mask 108 is placed only in the areaof one exhaust port 106. Preferably the mask 108 is located at theexhaust port 106 of the exhaust valve 106 a with prolonged opening time.It extends over an angle α of 150° to 180° around the center 106′ of thefirst exhaust port 106. The height HM of the mask 108 is 1.5 mm to 4 mm,as measured to half the height h of the valve disk rim 106 b. Thedistance a between the mask 108 and the valve disk rim 106 b is 0.3 mmto 0.7 mm.

FIG. 16 shows a diagram of valve lift H over crank angle KW, in whichthe valve lift curve of the intake valves 104 a, 105 a is designated byE. A₁ is the valve lift curve of the first exhaust valve 106 a, i.e.resulting from asymmetrical lifting, A₂ is the valve lift curve of thesecond exhaust valve 107 a. The opening flanks RÖ of the first exhaustvalve 106 a and the second exhaust valve 106 a are identical. Theclosing point AS₂ of the second exhaust valve 107 a, which differs fromthat of the first exhaust valve 106 a, is realized by an asymmetricalshape of the closing flank RS₁ of the first exhaust valve 106 a,relative to the opening flank. RS₂ designates the closing flank of thesecond exhaust valve 107 a. The different closing points AS₁ and AS₂ ofthe first and second exhaust valve 106 a, 107 a together with the commonopening point AÖ result in different opening periods Δt₁ and Δt₂.

The valve lift curve A₁′ shows a variant in which the closing point AS₁of the first exhaust valve 106 a also is later than the closing pointAS₂ of the second exhaust valve 107 a. In this case however opening andclosing flank RÖ′ and RS₁′ of the valve lift curve A₁′ are symmetrical.Here, too, different opening periods Δt₁ and Δt₂ of the first and secondexhaust valves lead to swirl formation in the combustion chamber.

The opening point AÖ is the same for both exhaust valves 106 a, 107 a.By synchronously opening the exhaust valves 106 a, 107 a at thebeginning of the exhaust stroke, high mass flow through the exhaustports 106, 107 into the exhaust duct is made possible, which is ofparticular importance at full load operation. Throttling losses can thusbe kept small and a power drop at full load is avoided.

A cylinder head 201 has for each cylinder 202 two intake ports 203opening into a combustion chamber 204. The openings 205 of the intakeports 203 are at least partially surrounded by masks 206 formed by thecylinder head 201, which are located on the intake side between theopenings 205 of both intake ports 203 and the wall of the combustionchamber 207. The purpose of the mask 206 is to enhance the intake tumbleflow and to direct it towards one side of the combustion chamber.

In FIG. 17 the contour 208 of the wall 213 of the mask 206 of an opening205 is shown in a developed view. Between two flanks 209, 210 thecontour has a main section 211 with maximum height HM. The contour 208of the mask 206 is asymmetrical, one of the two flanks 209, 210, i.e.flank 210 nearest to the cylinder rim 207, having a smallerslope—defined by the angle δ₂—than the other flank 209 nearer to thecylinder center 212. The slope angle of the other flank 209 isdesignated 61.

The main section 211 of the wall 213 of the mask 206 extends around thecenter 214 of the exhaust port over an angle α between 120° and 210°,with best results being obtained with an angle between 160° to 190°.

The direction 215 of the mask 206 is defined by a main axis 215 runningthrough the center M of the main section 211 of the wall 213 and thevalve center 214. The direction angle β₁, which is formed by the mainaxis 215 and a reference line 216 through the valve centers 214, has avalue approximately between 70° and 120°, preferably between 80° and110°. This will achieve an optimally developed tumble flow andparticularly good mixture preparation.

Reference numeral 217 designates the openings of the exhaust ports.

On the intake side an injector recess 218 is provided in the mask 206between the openings 205 of the intake ports 203, the distance a′between recess 218 and wall 213 being at least 1 mm, and with thesymmetry axis 219 a of the injection valve 219 forming an angle γ of 200to 300 with the cylinder head plane 221. It is essential that the jetcone 227 b of the injection jet 227 is distinctly kept away from thecombustion chamber top 222 and the cylinder wall. The center line 227 aof the injection jet 227 may also be slightly inclined against thesymmetry axis 219 a of the injection valve 219. The angle ε between thesymmetry axis 227 a of the injection jet 227 and the combustion chambertop 222 is roughly 33° to 40°. Due to this configuration the injectortip 220 may extend fairly deeply into the combustion chamber 204, whichwill permit precise fuel injection and will avoid wetting of thecombustion top face 222, of the opposite combustion chamber wall and ofthe intake valves 223.

The maximum height HM of the mask 206 is between 1.2 mm and 3.5 mmapproximately and is chosen such that at partial lift of the intakevalve 223 the intake opening between valve disk 224 and valve seat 225is essentially covered laterally except for a clearance 226 forming agap S. The gap S may have a width of 0.2 mm to 0.6 mm, preferably aquarter of the height HM of the mask 206 at most. When the valve lifth_(v) of the intake valve 223 exceeds 2.0 mm approximately, the intakeopening is freed also on the side of the mask 206, permitting maximumfilling of the cylinder especially at full load. In FIG. 21 the dottedlines show the maximum possible valve lift of the intake valve 223 atwhich the intake gap S between valve disk 224 and valve seat 225 willstill be just covered by the mask 206. The height of the valve disk rimis designated h. In the position shown the intake valve 223 extendsbeyond the mask by e=h/2. The height HM of the mask is thus thepredefined valve lift h_(v) plus half the height h of the valve diskrim.

It is of particular advantage if the cylinder head 201 is furnished witha device which permits valve lift to be fully variable, in which casethe merits of the mask 206 can be fully exploited.

1. Cylinder head for an internal combustion engine with at least twointake ports per cylinder opening into a combustion chamber, and perintake port with a valve seat located in the area of an opening, wherethe openings are partly surrounded by a mask formed by a materialprojection of the combustion chamber top face, wherein a contour of themask of at least one opening has a flat main section of maximum heightbetween an ascending and a descending flank and is asymmetrical in adeveloped view.
 2. Cylinder head according to claim 1, wherein theascending and the descending flanks of the contour have differentslopes.
 3. Cylinder head according to claim 1, wherein the flank of thecontour nearer a wall of the combustion chamber has a smaller slopeangle than a flank nearer a center of the combustion chamber. 4.Cylinder head according to claim 1, wherein the mask per opening extendsaround the center of the opening through an angle of approximately 120°to 210°.
 5. Cylinder head according to claim 1, wherein for each openinga main axis running through the middle of a main section of the maskforms a direction angle of 70° to 120°, with a reference line throughthe centers of the openings.
 6. Cylinder head according to claim 1,wherein a height of the mask is about 1.2 mm to 3.5 mm.
 7. Cylinder headaccording to claim 1, wherein there is a clearance between the mask anda disk of a lifting valve, which amounts to one fourth of the height ofthe mask at most.
 8. Cylinder head according to claim 1, wherein aninjection device enters in the area of the mask between openings, themask having an injection recess in a region of an injector tip. 9.Cylinder head according to claim 1, wherein a depth of the injectionrecess corresponds to about the height of the mask at most.
 10. Cylinderhead according to claim 1, wherein the injection recess has a certaindistance from a wall of the mask, this distance being at least 1 mm.